SVT Flashcards
You are the medical SHO on-call. You have been asked to see a 72 year old man in A+E resus. He has presented with chest pain and tachycardia. On arrival you are presented with the following ECG:
The patient’s current observations: BP: 130/80 HR: 150 RR: 22 Sats: 96% on room air T: 36.8 degrees
What does the ECG show?
When answering, show your examiners that you know what you’re looking for. The answer here is supraventricular tachycardia (SVT) however you should ensure you show them how you are working this out
- This ECG shows a supraventricular tachycardia
- A regular rhythm, in tachycardia (150 bpm)
- P waves are not visible, potentially hidden
- Narrow QRS
- No ST segment changes (check all leads)
P wave may be either buried in T waves or occur after QRS complex
What causes of SVT would you be thinking about before you approached this patient?
C - Cardiac
- MI
- HF
- Cardiomyopathy - anything interfering wiht the conduction system
R - Respiratory
- PE
I - Infection
- Chest, urine, respiratory, sepsis
M - Metabolic
- Thyroid (hyperT, thyrotoxicosis)
E - Electrolyte
- hypoK, hyperK
- hypoM
D - Drugs
- Caffeine
- Alcohol
- Beta-agonists (salbutamol)
- Amphetamines
P - Pain
V - Volume loss
* Anaemia
* GI losses
How would you manage this patient?
My Mx of tachycardia would be determined by whether the patient is stable or unstable, the type of tachycardia and the likely cause.
I would use an ABCDE approach in the first instance to establish this.
A
- Ensure patent airway
B
- continuous SpO2 monitoring, give O2 if SpO2 < 94%
- auscultate
C
- Check HR, BP, CRT
- 12-lead ECG - identify rhythm
- Obtain IV access - fluid challenge to see if tachycardia is fluid-responsive
- Identify and treat reversible causes if the rhythm is sinus tachycardia
D
- Check blood sugar and temperature
If the rhythm is SVT and the patient is unstable
- Shock (sBP < 90 mmHg)
- Chest pain / ischaemia on ECG
- Pulmonary oedema
- Syncope
it would be at this instance that I would put out a crash call
If the patient is stable, I would attempt to reverse the SVT using the vagal maoeuvres if the pt is able to
If not, escalate to senior and proceed to medical management
- Adenosine 6 mg IV into a large vein followed by 0.9% saline flush, while recording a rhythm strip
- Repeat after 2 min, give 12 mg IV
- Repeat after 2 min, give 18 mg IV
I would warn the patient about the unpleasant side effects (impending sense of doom, dyspnoea, chest tightness, headache)
Continue to reassess the patient using A to E approach.
If initial measures unsuccessful, escalate to my senior. If at any point patient becomes unstable > crash call
What investigations would you want to do?
Bedside
- 12-lead ECG
- Monitor BP
- VBG/ABG (quickly alert me to electrolyte imbalance)
Bloods
- VBG, FBC, U&E + Mg, TFTs, LFTs, Bone profile, CRP, Troponin
- If infection likely - blood cultures, urine MC&S, sputum MC&S if appropriate
Imaging
- CXR
- Echo
- 24 hour tape
What medications could you use in this patient?
The appropriate medication to give in SVT is adenosine
* Causes a transient heart block
* Mediated by A1 receptors
* Used to identify the underlying rhythm
* Very short half-life
Contraindications
- 2nd or 3rd degree heart block without a pacemaker
- Long QT syndrome
- Decompensated heart failure
- Asthma
How much?
- 6 mg IV, wait 2 min, if unsuccessful cardioversion
- 12 mg IV, wait 2 min, if unsuccessful cardioversion
- 18 mg IV
Did they convert? If so, tachycardia can be considered NODAL in origin
If it is ATRIAL in origin, adenosine will only transiently block it, usually then reverts back
What would you tell the patient before giving them adenosine?
Before giving
Explain pt may experience
- Flushing
- Nausea
- Light-headedness associated with a ‘sense of impending doom’
- All secondary to transient asystole following IV administration
You have given the patient 3 doses of adenosine, but they always reverted back to tachycardia. What do you do now?
Assuming the patient continues being stable, since they reverted back to tachycardia following adenosine, we can now treat with longer acting AV node blockers
Beta-blockers (metoprolol, esmolol)
- CId in severe asthma, COPD
Calcium Channel Blockers (diltiazem, verapamil)
- CId in HFrEF (negative inotropic effect)
The patient starts becoming hypotensive, with a BP of 80/50 mmHg, HR 170 bpm, and SpO2 88%. What would you do now?
Put out an emergency call / MET call and call senior
As per ALS guidelines, since in SVT and haemodynamically unstable, the patient would be sedated and get DC cardioversion
How do you differentiate SVTs?
SVTs can be broken down by site of origin and rhythm regularity
Is the SVT atrial or atrioventricular in origin?
Is the rate regular or irregular?
You now have one minute to handover the patient in this scenario to your registrar/consultant as if you were at the Acute Medical Handover.
Situation: This is a 72 year old man who is in SVT and has now become unstable with hypotension.
Background: The gentleman initially presented to A+E with chest pain and was tachycardic but initially maintaining his blood pressure. He has not received any other medications.
Assessment: A full ABCDE assessment has been carried out and investigations have been sent for common causes of SVT.
Recommendations: I have put out a 2222 cardiac arrest call. I need urgent medical assistance. As per the resuscitation guidelines this gentleman is likely to need DC cardioversion and I will need support from my senior colleagues to carry this out. Due to the hypotension this would now be the preferred management of the SVT rather than medical management.
